I recently ordered a 4gb memory upgrade for my 2008 mac pro. Since installing it, there's been a noticeable speed increase that I'm really happy with, but the "About This Mac" page says it is 667mhz - not the 800mhz that's marked on the product page and on the package it came in. Is there anything that could cause it to show up as 667mhz, other than just being the wrong part? How much difference does the speed difference make? I could have it replaced, although I'm not sure if the replacement would have the same problem. I could also get a refund and buy the memory somewhere else, but that may not be worth it - for example OWC changes $120 for the same 4gb that I spent $45 on. Any advice would be appreciated!